vim-gtk3: Fix gtk3 build after gtk3 3.24.1 update

vim-gtk3 was affected by a problem similar to PR pkg/53688, and
the test failed to recognize gtk3 due `undefined reference to
`epoxy_has_glx'' when `checking for GTK - version >= 3.0.0' in the
configure phase because instead of linking to pkgsrc libepoxy it
linked against builtin libepoxy.  Despite that it successfully
built without gtk3 support but gvim failed at run time with
`E25: GUI cannot be used: Not enabled at compile time' error.

Sort x11 bl3 includes so instead of failing at run time it fails
at build time when linking vim.

Add a kludge to override `--x-libraries' and `--x-includes' passed
by x11.buildlink3.mk to avoid linking against builtin libepoxy and
fix gtk3 support.

Thanks to <Rhialto>!

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/editors/vim-gtk3/Makefile,v
retrieving revision 1.12
diff -u -p -r1.12 Makefile
--- Makefile	14 Nov 2018 22:21:24 -0000	1.12
+++ Makefile	30 Dec 2018 19:59:55 -0000
@@ -40,9 +40,16 @@ post-install:
 
 .include "../../converters/libiconv/buildlink3.mk"
 .include "../../devel/gettext-lib/buildlink3.mk"
+.include "../../x11/gtk3/buildlink3.mk"
 .include "../../x11/libXpm/buildlink3.mk"
 .include "../../x11/libXt/buildlink3.mk"
-.include "../../x11/gtk3/buildlink3.mk"
+
+# XXX: `--x-libraries' and `--x-includes' are injected to CONFIGURE_ARGS via
+# XXX: mk/x11.buildlink3.mk. Override them by redefining them to NONE in order
+# XXX: to avoid picked up possible undesidered libraries similarly to
+# XXX: PR pkg/53688.
+CONFIGURE_ARGS+=	--x-libraries=NONE
+CONFIGURE_ARGS+=	--x-includes=NONE
 
 .include "../../mk/termcap.buildlink3.mk"
 .include "../../mk/bsd.pkg.mk"